I used to listen to nothing but FLAC/320kcbr on my Onkyo TX-NR717 and Schiit Asgard 2, but I came across a bunch of old CD's and do not want to rip them. Since my Onkyo has a DAC does this mean I don't need to buy a 'good' CD player? One that doesn't have it's own DAC? I have Sennheiser HD600's as well so I am definitely not wanting my CD player to be the weak link in my headphone set-up. If I do end up buying a CD player with a DAC, how do I tell my system to use the one in my Onkyo, rather than the one inside the CD player? Thanks in advance for your time/help.

Virtually all CD players have DACs. if you get one with a digital output you can use that to send the data to your AVR's DAC. My advice is to get a Blu Ray player instead. It will be less expensive, do the same job and even allow you to play videos if you like. If your AVR or preamp has a headphone output, that should work the same as a dedicated headphone amp. All of these devices have noise and other issues well below the level of audibility.